This is the Cave Tileset pack (original link) created by Clint Bellanger, contributor of opengameart.org. According to the author, below is a description of this pack:
- Two variety of straight, convex, concave base walls rendered four directions
- Additional wall styles featuring spiderwebs, stalagmites, mushrooms, and mine shaft supports
- 16 base floor tiles (best used in a repeating 4×4 grid)
- Minecart tracks and carts
- Floor rubble, bones, stalagmites, and stalactite-pillars
- Simple water tiles
License
This  pack is licensed under the Creative Commons Attribution Share Alike 3.0 License,  GNU General Public License 3 and  GNU General Public License 2.
Art attributions
If you use this pack, please include the following attribution in a visible location along with any other credits:
"Cave Tileset" art by Clint Bellanger (opengameart.org)
When possible link to page that presents the original art collection. For this asset pack, it would be “Cave Tileset” art by Clint Bellanger (opengameart.org).
About the artist
Clint Bellanger
I am a software developer at the Auburn University Libraries in Auburn, Alabama. I am a graduate of Louisiana Tech University in CS. 3D skills: Low-poly mesh modeling, rigging, UV mapping, animation.
New: Assets Pack #5 – Cave Tileset, by @clintbellanger http://t.co/RCtlUJIA #gamedev #free #assets